This invention relates to a semiconductor article suitable for use in the detection of hydrogen gas in the atmosphere.
Because of the high combustibility of hydrogen, it is important that the presence of the gas be detected at relatively low concentrations on the order of 10 ppm. Although there are a number of analytical devcies which can accurately measure hydrogen at low concentrations, such equipment generally does not lend itself to field testing.
Hydrogen is often stored in large tanks or other containers situated in locations where the transportation of bulky analytical equipment is rendered impractical. Thus, the need for lightweight sensors, which can accurately detect the presence of hydrogen in the atomosphere at relatively low concentrations such as caused by a leak in the storage tank, has become apparent.
One prior lightweight sensor is disclosed in "Hydrogen Leak Detector Using a Pd-gate MOS Transistor, " by L. Stiblert and C. Svensson, published in Rev. Sci. Instrum., vol. 46, No. 9, September 1975. The device therein disclosed uses a conventional FET with the gate electrode comprised of palladium, and a temperature stabilizing circuit so the sensor can be operated at temperatures on the order of 150.degree. C. The transistor comprises silicon and silicon dioxide. Also, a conventional FET device operates on the principleof electrostatic charge whereas the device of the present invention operates on a different mechanism, as discussed hereinafter.
It is therefore, an object of the present invention to provide a semiconductor article suitable for detecting the presence of low concentration of hydrogen in the atmosphere.
This and other objects and advantage are obtained by forming a thin film semiconductor article comprising a semiconductor detecting film having an activation film disposed thereon, a resistance means, and a thermistor. The semicondutor film principally comprises a thin layer of stannic oxide which may be doped with an impurity such as indium, to change the film conductivity. The semiconductor film is deposited onto one side of an inert refractory chip. A thermistor is also disposed onto this side of the chip. The resistance heating means is disposed onto this side of the chip. A thermistor is also disposed onto this side of the chip. The detecting film and the resistance heater are connected into separate, isolated circuits. The chip is then mounted onto an inorganic foam substrate.